A 58-year-old woman with primary angle closure glaucoma (PACG) has an IOP of 42 mmHg despite maximum topical therapy. She has a shallow anterior chamber with a patent peripheral iridotomy. Gonioscopy reveals more than 180 degrees of peripheral anterior synechiae (PAS). Plateau iris configuration is suspected on UBM. Which of the following mechanisms BEST explains the persistent angle closure despite a patent iridotomy?
- A Pupillary block due to incomplete iridotomy
- B Zonular laxity causing anterior lens subluxation
- C Anteriorly rotated ciliary body with forward displacement of peripheral iris ✓
- D Aqueous misdirection into the vitreous cavity
Correct answer: C. Anteriorly rotated ciliary body with forward displacement of peripheral iris
Explanation
Plateau iris configuration is caused by anteriorly positioned and anteriorly rotated ciliary body processes that mechanically push the peripheral iris forward to occlude the angle — this is non-pupillary-block mechanism. Even with a patent iridotomy (which relieves pupillary block), the angle remains occluded due to this ciliary process configuration. Aqueous misdirection causes a completely shallowed chamber; zonular laxity causes phacodonesis.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.